Assessment of dental fluorosis in Mmp20 +/- mice

The molecular mechanisms that underlie dental fluorosis are poorly understood. The retention of enamel proteins hallmarking fluorotic enamel may result from impaired hydrolysis and/or removal of enamel proteins. Previous studies have suggested that partial inhibition of Mmp20 expression is involved in the etiology of dental fluorosis. Here we ask if mice expressing only one functional Mmp20 allele are more susceptible to fluorosis. We demonstrate that Mmp20 (+/-) mice express approximately half the amount of MMP20 as do wild-type mice. The Mmp20 heterozygous mice have normal-appearing enamel, with Vickers microhardness values similar to those of wild-type control enamel. Therefore, reduced MMP20 expression is not solely responsible for dental fluorosis. With 50-ppm-fluoride (F(-)) treatment ad libitum, the Mmp20 (+/-) mice had F(-) tissue levels similar to those of Mmp20 (+/+) mice. No significant difference in enamel hardness was observed between the F(-)-treated heterozygous and wild-type mice. Interestingly, we did find a small but significant difference in quantitative fluorescence between these two groups, which may be attributable to slightly higher protein content in the Mmp20 (+/-) mouse enamel. We conclude that MMP20 plays a nominal role in dental enamel fluorosis.

Fluoride's effects on the formation of teeth and bones, and the influence of genetics

Fluorides are present in the environment. Excessive systemic exposure to fluorides can lead to disturbances of bone homeostasis (skeletal fluorosis) and enamel development (dental/enamel fluorosis). The severity of dental fluorosis is also dependent upon fluoride dose and the timing and duration of fluoride exposure. Fluoride's actions on bone cells predominate as anabolic effects both in vitro and in vivo. More recently, fluoride has been shown to induce osteoclastogenesis in mice. Fluorides appear to mediate their actions through the MAPK signaling pathway and can lead to changes in gene expression, cell stress, and cell death. Different strains of inbred mice demonstrate differential physiological responses to ingested fluoride. Genetic studies in mice are capable of identifying and characterizing fluoride-responsive genetic variations. Ultimately, this can lead to the identification of at-risk human populations who are susceptible to the unwanted or potentially adverse effects of fluoride action and to the elucidation of fundamental mechanisms by which fluoride affects biomineralization.

Influence of genetic background on fluoride metabolism in mice

A/J and 129P3/J mouse strains have different susceptibilities to dental fluorosis, due to their genetic backgrounds. This study tested whether these differences are due to variations in water intake and/or F metabolism. A/J (susceptible to dental fluorosis) and 129P3/J mice (resistant) received drinking water containing 0, 10, or 50 ppm F. Weekly F intake, excretion and retention, and terminal plasma and femur F levels were determined. Dental fluorosis was evaluated clinically and by quantitative fluorescence (QF). Data were tested by two-way ANOVA. Although F intakes by the strains were similar, excretion by A/J mice was significantly higher due to greater urinary F excretion, which resulted in lower plasma and femur F levels. Compared with 129P3/J mice given 50 ppm F, significantly higher QF scores were recorded for A/J mice. In conclusion, these strains differ with respect to several features of F metabolism, and amelogenesis in the 129P3/J strain seems to be unaffected by high F exposure.

Modulation of murine bone marrow-derived CFU-F and CFU-OB by in vivo bisphosphonate and fluoride treatments

OBJECTIVES

Bisphosphonates (BPN) have actions on a variety of cell types including: osteoclasts, osteoblasts, osteocytes, and endothelial cells. The objectives of this report are to review the current state of understanding of the effects of BPNs on orthodontic tooth movement and to provide evidence on BPN's in vivo effects on bone marrow-derived osteoprogenitor cells.

MATERIAL AND METHODS

Mice from the C3H/HeJ (C3H), C57BL/6J (B6), FVB/NJ (FVB), and BALB/cByJ (BALB) strains were treated for 3 weeks with 0, 3, 30, or 150 mcg/kg/week alendronate (ALN) administered subcutaneous alone or in combination with 50 ppm fluoride (F). Bone marrow cells were harvested and subjected to in vitro colony-forming unit fibroblast (CFU-F) and colony-forming unit osteoblasts (CFU-OB) assays.

RESULTS

Baseline differences in CFU-F, CFU-OB/ALP+, and CFU-OB/total were observed among the four strains. Strain-specific responses to ALN and F treatments were observed for CFU-F, CFU-OB/ALP+, and CFU-OB/total. F treatment alone resulted in decreases in CFU-F (p = 0.013), CFU-OB/ALP+ (p = 0.005), and CFU-OB/total (p = 0.003) in the C3H strain. CFU-F (p = 0.036) were decreased by F in the B6 strain. No significant (NS) effects of F were observed for FVB and BALB. ALN treatment resulted in a significant decrease in CFU-F (p = 0.0014) and CFU-OB/total (p = 0.028) in C3H only. ALN treatment had NS effect on CFU-OB/ALP+ in all four strains.

CONCLUSION

Genetic factors appear to play a role in ALN's effects on CFU-F and CFU-OB/total but not on CFU-OB/ALP+.

Fluoride effects on bone formation and mineralization are influenced by genetics

INTRODUCTION

A variation in bone response to fluoride (F(-)) exposure has been attributed to genetic factors. Increasing fluoride doses (0 ppm, 25 ppm, 50 ppm, 100 ppm) for three inbred mouse strains with different susceptibilities to developing dental enamel fluorosis (A/J, a "susceptible" strain; SWR/J, an "intermediate" strain; 129P3/J, a "resistant" strain) had different effects on their cortical and trabecular bone mechanical properties. In this paper, the structural and material properties of the bone were evaluated to explain the previously observed changes in mechanical properties.

MATERIALS AND METHODS

This study assessed the effect of increasing fluoride doses on the bone formation, microarchitecture, mineralization and microhardness of the A/J, SWR/J and 129P3/J mouse strains. Bone microarchitecture was quantified with microcomputed tomography and strut analysis. Bone formation was evaluated by static histomorphometry. Bone mineralization was quantified with backscattered electron (BSE) imaging and powder X-ray diffraction. Microhardness measurements were taken from the vertebral bodies (cortical and trabecular bones) and the cortex of the distal femur.

RESULTS

Fluoride treatment had no significant effect on bone microarchitecture for any of the strains. All three strains demonstrated a significant increase in osteoid formation at the largest fluoride dose. Vertebral body trabecular bone BSE imaging revealed significantly decreased mineralization heterogeneity in the SWR/J strain at 50 ppm and 100 ppm F(-). The trabecular and cortical bone mineralization profiles showed a non-significant shift towards higher mineralization with increasing F(-) dose in the three strains. Powder X-ray diffraction showed significantly smaller crystals for the 129P3/J strain, and increased crystal width with increasing F(-) dose for all strains. There was no effect of F(-) on trabecular and cortical bone microhardness.

CONCLUSION

Fluoride treatment had no significant effect on bone microarchitecture in these three strains. The increased osteoid formation and decreased mineralization heterogeneity support the theory that F(-) delays mineralization of new bone. The increasing crystal width with increasing F(-) dose confirms earlier results and correlates with most of the decreased mechanical properties. An increase in bone F(-) may affect the mineral-organic interfacial bonding and/or bone matrix proteins, interfering with bone crystal growth inhibition on the crystallite faces as well as bonding between the mineral and organic interface. The smaller bone crystallites of the 129P3/J (resistant) strain may indicate a stronger organic/inorganic interface, reducing crystallite growth rate and increasing interfacial mechanical strength.

The genetic influence on bone susceptibility to fluoride

INTRODUCTION

The influence of genetic background on bone architecture and mechanical properties is well established. Nevertheless, to date, only few animal studies explore an underlying genetic basis for extrinsic factors effect such as fluoride effect on bone metabolism.

MATERIALS AND METHODS

This study assessed the effect of increasing fluoride doses (0 ppm, 25 ppm, 50 ppm, 100 ppm) on the bone properties in 3 inbred mouse strains that demonstrate different susceptibilities to developing enamel fluorosis (A/J a "susceptible" strain, 129P3/J a "resistant" strain and SWR/J an "intermediate" strain). Fluoride concentrations were determined in femora and vertebral bodies. Bone mineral density was evaluating through DEXA. Finally, three-point bend testing of femora, compression testing of vertebral bodies and femoral neck-fracture testing were performed to evaluate mechanical properties.

RESULTS

Concordant with increasing fluoride dose were significant increases of fluoride concentration in femora and vertebral bodies from all 3 strains. Fluoride treatment had little effect on the bone mineral densities (BMD) in the 3 strains. Mechanical testing showed significant alterations in "bone quality" in the A/J strain, whereas moderate alterations in "bone quality" in the SWR/J strain and no effects in the 129P3/J strain were observed.

CONCLUSION

The results suggest that genetic factors may contribute to the variation in bone response to fluoride exposure and that fluoride might affect bone properties without altering BMD.

Assessment of teeth as biomarkers for skeletal fluoride exposure

Skeletal fluorosis and dental fluorosis are diseases related to fluoride (F) ingestion. Bone is the largest storage site of F in our body. Therefore, bone F concentrations are considered biomarkers for total F body burden (exposure). However, difficult accessibility limits its use as a biomarker. Thus, a more accessible tissue should be considered and analyzed as a biomarker for total F body burden. The objective of this study, which was divided into two parts, was to evaluate teeth as a biomarker for skeletal F exposure. In part 1 of the study, 70 mice of three different strains (SWR/J, A/J and 129P3/J) were exposed to different levels of water fluoridation (0, 25, 50 and 100 ppm). Bone (femora and vertebrae) and teeth from these mice were then analyzed for F concentration using Instrumental Neutron Activation Analysis (INAA). In part 2 of the study, human teeth (enamel and dentin) and bone from 30 study subjects were collected and analyzed for F concentration using INAA. Study subjects lived in areas with optimum levels of water fluoridation (0.7 and 1 ppm) and underwent therapeutic extraction of their unerupted third molars. The values of bone and teeth F concentration were correlated for parts 1 and 2 of this study. The results showed that in the animal model, where animals were exposed to a wide range of F in their drinking water, tooth [F] correlated with bone [F]. However, no correlation was seen between bone and enamel F concentrations or between bone and dentin F concentrations in the human samples. Therefore, teeth are not good biomarkers for skeletal F exposure in humans when exposure is confined to optimum levels of F in the drinking water.

Neurofibromin and its inactivation of Ras are prerequisites for osteoblast functioning

Skeletal problems and osteoporosis occur in up to 50% affected neurofibromatosis type 1 (NF1) humans. Inactivation of neurofibromin results in deregulation of Ras signal transduction. Little is known of bone biology in humans with NF1. The goal of our work was to determine if loss-of-function of Nf1 gene was associated with altered bone homeostasis and Ras signal transduction. Because homozygous Nf1 mice are embryonically lethal, heterozygote Nf1 (Nf1+/-) male mice were used to investigate skeletal phenotypes and osteoprogenitor functions, using standard in vivo and in vitro assays. We found that bone mass and geometry of Nf1+/- mice did not differ from wild type controls, despite a trend to less bone formation. Nf1+/- committed osteoprogenitors from femur metaphysis exhibited premature apoptosis and higher proliferation. Ras signaling was activated in primary Nf1+/- bone marrow-inducible osteoprogenitors. Inducible osteoprogenitors exhibited lower induction of osteoblast differentiation, assessed as alkaline phosphatase positive CFU-f. A screen of osteoblast marker genes showed a selective increase in osteopontin (OPN) mRNA and protein expression in these cells. OPN protein was increased in Nf1+/- bone, especially in cortical bone matrix. Because bone cell abnormalities in Nf1 haploinsufficiency were detected in vitro, redundant pathways must compensate for the deregulation of Ras signaling in vivo to maintain normal bone mass and function in vivo. Our in vitro data revealed that neurofibromin and its control of Ras signaling are required for osteoprogenitor homeostasis.

Tooth quality in dental fluorosis genetic and environmental factors

Dental fluorosis (DF) affects the appearance and structure of tooth enamel and can occur following ingestion of excess fluoride during critical periods of amelogenesis. This tooth malformation may, depending on its severity, influence enamel and dentin microhardness and dentin mineralization. Poor correlation between tooth fluoride (F) concentration and DF severity was shown in some studies, but even when a correlation was present, tooth fluoride concentration explained very little of DF severity. This fact calls into question the generally accepted hypothesis that the main factor responsible for DF severity is tooth fluoride concentration. It has been shown previously that genetic factors (susceptibility to DF) play an important role in DF severity although DF severity relates to individual susceptibility to fluoride exposure (genetics), tooth fluoride concentration relates to fluoride ingestion (environmental). The objective of this study was to investigate the correlation between tooth fluoride concentration, DF severity, and tooth mechanical and materials properties. Three strains of mice (previously shown to have different susceptibility to DF) at weaning were treated with four different levels of F in their water (0, 25, 50, and 100 ppm) for 6 weeks. Mice teeth were tested for fluoride by instrumental neutron activation analysis (INAA), DF severity determined by quantitative light-induced fluorescence [QLF], and tooth quality (enamel and dentin microhardness and dentin mineralization). Tooth fluoride concentration (environment factor) correlated positively with DF severity (QLF) (rs=0.608), fluoride treatment group (rs=0.952). However, tooth fluoride concentration correlated negatively with enamel microhardness (rs=-0.587), dentin microhardness (rs=-0.268) and dentin mineralization (rs=-0.245). Dental fluorosis (genetic factor) severity (QLF) correlated positively with fluoride treatment (rs=0.608) and tooth fluoride concentration (rs=0.583). DF severity correlated negatively with enamel microhardness (rs=-0.564) and dentin microhardness (rs=-0.356). Genetic factors (DF severity) and the environmental factor (fluoride concentration in tooth structure) have similar influence on tooth biomechanical properties, whereas only the environmental factor has an influence on tooth material property (mineralization).

The tight skin mouse: an animal model of systemic sclerosis

The search for an animal model of systemic sclerosis (SSc) was tenaciously pursued by E.C. LeRoy. We studied several aspects of the tight skin mouse (Tsk) genetics and pathogenesis under his stimulating influence that contributed to a better understanding of the fibrotic scleroderma-like phenotype of this mouse. The identification of the fibrillin-1 mutation in the Tsk mouse and the characterization of the cellular and molecular pathways leading to Tsk fibrosis by numerous research groups has opened new avenues in the investigation of human SSc. The enigmatic connections between autoimmunity and ECM homeostasis in fibrotic diseases have received extensive attention in this mouse in which a prirmary alteration of a connective tissue microfibrilar protein leads to the reproduction of cellular and autoimmune abnormalities strikingly similar to human SSc. The use of this mouse as a tool to explore anti-fibrotic therapeutic interventions has demonstrated its value in providing useful information on the search for a therapy for this untreatable facet of human disease.

Genetic predisposition to external apical root resorption in orthodontic patients: linkage of chromosome-18 marker

External apical root resorption (EARR) is a common orthodontic treatment sequela. Previous studies implicate a substantial genetic component for EARR. Using a candidate gene approach, we investigated possible linkage of EARR associated with orthodontic treatment with the TNSALP, TNFalpha, and TNFRSF11A gene loci. The sample was comprised of 38 American Caucasian families with a total of 79 siblings who completed comprehensive orthodontic treatment. EARR was assessed by means of pre- and post-treatment radiographs. Buccal swab cells were collected for extraction and analysis of DNA. No evidence of linkage was found with EARR and the TNFalpha and TNSALP genes. Non-parametric sibling pair linkage analysis identified evidence of linkage (LOD = 2.5; p = 0.02) of EARR affecting the maxillary central incisor with the microsatellite marker D18S64 (tightly linked to TNFRSF11A). This indicates that the TNFRSF11A locus, or another tightly linked gene, is associated with EARR.

Dental fluorosis: variability among different inbred mouse strains

Concurrent with the decline in dental caries has been an increase in the prevalence of dental fluorosis, a side-effect of exposure to greater than optimal levels of fluoride during amelogenesis. The mechanisms that underlie the pathogenesis of dental fluorosis are not known. We hypothesize that genetic determinants influence an individual's susceptibility or resistance to develop dental fluorosis. We tested this hypothesis using a mouse model system (continuous eruption of the incisors) where genotype, age, gender, food, housing, and drinking water fluoride level can be rigorously controlled. Examination of 12 inbred strains of mice showed differences in dental fluorosis susceptibility/resistance. The A/J mouse strain is highly susceptible, with a rapid onset and severe development of dental fluorosis compared with that in the other strains tested, whereas the 129P3/J mouse strain is least affected, with minimal dental fluorosis. These observations support the contribution of a genetic component in the pathogenesis of dental fluorosis.

Analysis of the EPHX1 113 polymorphism and GSTM1 homozygous null polymorphism and oral clefting associated with maternal smoking

Maternal cigarette smoking during the first trimester of pregnancy is associated with an increased risk of having a child with an oral cleft. Compounds present in cigarette smoke undergo bioactivation and/or detoxication. Phase I of this process results in the formation of reactive epoxides, which can form DNA adducts initiating and promoting mutagenesis, carcinogenesis, or teratogenesis. Microsomal epoxide hydrolase (mEH; gene symbol EPHX1) catalyzes hydrolysis of epoxides. Phase II involves attachment of a moiety (e.g., glutathione) to the compound mediated by a variety of enzymes, including glutathione S-transferase, generally resulting in a decreased reactivity. Recent studies suggest an association between the EPHX1 codon 113 polymorphism or homozygous null GSTM1 allele and the risk of carcinogenesis, emphysema, phenytoin-associated oral clefting, and the risk of spontaneous abortion. This study explores the association between EPHX1 codon 113 and homozygous null GSTM1 genotypes and oral clefting among infants whose mothers smoked during pregnancy. Case infants were diagnosed with isolated cleft lip with or without cleft palate (CL/P). EPHX1 codon 113 allelotyping was performed on 195 samples (85 cases, 110 controls) by PCR/RFLP analysis. 130 samples (79 cases, 51 controls) were tested for the GSTM1 homozygous null genotype using PCR. Using the odds ratio as a measure of association, we did not observe elevated risks of CL/P associated with either allelic comparison. This suggests that when mothers smoke periconceptionally, their infants having these alleles at either (or both) loci were not at substantially increased risk for CL/P compared to infants with the wild-type alleles.

The Ephx1(d) allele encoding an Arg338Cys substitution is associated with heat lability

Heat lability of the mouse hepatic microsomal epoxide hydrolase 1 enzyme-specific activity (EC 3.3.2.3) is greater for the A/J than the C57BL/6J strain. Analysis of the microsomal epoxide hydrolase 1 cDNA coding sequences shows the C57BL/6J and A/J strains to differ in a single base, a C to T transition at position 1012 from the ATG. This change would predict a substitution of an Arg for a Cys at codon 338. Lyman et al. (J. Biol. Chem 255:8650, 1980) studied 26 inbred mouse strains and assigned each strain to one of two groups based upon functional criteria that included heat lability and pH optima for microsomal epoxide hydrolase 1. The heat-labile strains including A/J were denoted with the Ephx1(d) allele, whereas C57BL/6J and other members of the heat-stable strains were denoted with the Ephx1(b) allele. We examined those same inbred mouse strains and found complete concordance between the assignment of microsomal epoxide hydrolase 1 allele superscript "b" or "d" and the wild-type and C1012T polymorphism respectively (Fisher's Exact Test, two-sided p < 0.0001). These data suggest that mouse hepatic microsomal epoxide hydrolase 1 heat lability is associated with the presence of a Cys at residue 338. Genomic samples from the available AXB and BXA recombinant inbred strains were allelotyped for the SNP identified in the Ephx1 gene that distinguishes the A/J and C57BL/6J parental strains and used to map Ephx1 to Chromosome (Chr) 1 at approximately 98.5cM (LOD = 10.0).

A novel FGFR2 gene mutation in Crouzon syndrome associated with apparent nonpenetrance

OBJECTIVE

To determine whether specific mutations within the fibroblast growth factor receptor 2 (FGFR2) gene that are associated with Crouzon syndrome can be present in an individual who had been assumed to be "clinically normal."

METHODS

Most mutations responsible for Crouzon syndrome occur in exons IIIa (U) or IIIc (B) of the FGFR2 gene, which facilitates allelotyping using polymerase chain reaction (PCR)-mediated mutation analysis. Once a specific mutation was identified in the index case, remaining affected family members and "clinically normal" first-degree relatives were analyzed in order to correlate genotype with phenotype.

RESULTS

A novel missense mutation--a G to T transversion--involving the first base of codon 362 was identified in all Crouzon syndrome-affected family members and in one "clinically normal"-appearing parent following DNA sequencing of exon B of the FGFR2 gene and specific BstNI restriction fragment length polymorphism. Pattern profile analysis demonstrated a consistent collection of abnormal cephalometric measurements in the Crouzon-affected family members and, to a lesser degree, in the "clinically normal" parent.

CONCLUSION

We have identified a novel missense mutation in the FGFR2 gene that predicts an Ala362Ser substitution shared by all family members affected by Crouzon syndrome and by a "clinically normal"-appearing father. These data support nonpenetrance of Crouzon syndrome when the diagnosis is based on clear clinical findings. Only through cephalometry was there an indication of minimal expression of Crouzon syndrome in the "clinically normal"-appearing father.

Thrombospondin 1 is expressed by mesenchymal cells in mouse post-natal skin and hair follicle development

Thrombospondin 1 is an extracellular matrix glycoprotein with multiple functions. In the skin, it has been immunolocalized to basement membrane, and its expression increases during embryogenesis and wound healing. Its normal cellular source in the skin is not known, except during wound healing, where macrophages and keratinocytes seem to be the primary source. We have analysed the expression of thrombospondin 1 mRNA in normal mouse skin at different ages by in situ hybridization. It was found that the mRNA is expressed by dermal mesenchymal cells and mature fibroblasts and developmentally regulated during post-natal skin growth and morphogenesis. In adult mouse skin, expression of the thrombospondin is restricted to the mesenchymal cells of hair follicle papilla. These results suggest that the regulation of thrombospondin 1 transcription in mesenchymal cells can play an important role in post-natal skin development. Its mRNA expression is a characteristic of adult dermal papilla cells with a potential role in hair development.

Overexpression of human stem cell factor impairs melanocyte, mast cell, and thymocyte development: a role for receptor tyrosine kinase-mediated mitogen activated protein kinase activation in cell differentiation

Stem cell factor (SCF) is synthesized as both soluble (S) and membrane-associated (MA) proteins. Indirect insight into the function of MA and S isoforms of SCF has come from studies performed in Steel (Sl) mutant mice. However, the physiologic role(s) of these two isoforms remain unknown. In an attempt to better understand the in vivo role of c-kit/SCF interactions on various cell lineages, transgenic mice were generated that overexpress MA isoform of human SCF (hSCF). In murine cells, hSCF behaves as an antagonist to normal SCF function, due to interference with the interaction between endogenous murine SCF and its receptor, c-kit, encoded by the dominant white spotting (W) gene. Mice expressing the hSCF transgene display a variety of phenotypic abnormalities, which are accentuated when combined with W alleles. Here we show that mice homozygous for the hSCF transgene demonstrate a coat color deficiency seen in some mice homozygous for mild W alleles. Specifically, homozygous hSCF transgenic mice (hSCF220) display a pronounced forehead blaze, with additional white spots over the cervical region, as well as a very large belly spot. Doubly heterozygous animals that carry both a mutated W allele and the hSCF transgene also display an unusual pigment defect and a dramatic reduction in the number of dermal mast cells. Furthermore, overexpression of MA hSCF in the thymus results in abnormal thymocyte differentiation and proliferation, which is associated with reduced mitogen activated protein (MAP) kinase activation. Thus, MAP kinase activation by a receptor tyrosine kinase, such as c-kit, may be critical for the differentiation of thymocytes in vivo.

Murine interleukin-11 (IL-11) is expressed at high levels in the hippocampus and expression is developmentally regulated in the testis

IL-11, derived from a bone marrow stromal cell line, has pleiotropic effects on both hematopoietic cells and nonhematopoietic cells. However, no previous studies have systematically addressed expression of IL-11 in primary tissues in vivo and the relationship of IL-11 tissue specific gene expression and function of IL-11 is not clear. In the present study, we examined constitutive IL-11 expression in various murine adult tissues in vivo. IL-11 mRNA is expressed in a wide range of normal tissues (including hematopoietic organs) at levels only detected by RT-PCR. IL-11 protein was detected in brain and testis by Western blot analysis. The in vivo cellular distribution of IL-11 expression was examined by in situ hybridization. In brain, IL-11 message is distributed in granular layer dentate gyrus and pyramidal cell layers of hippocampus. IL-11 is also expressed in anterior horn cells and lateral column neuronal cells of the spinal cord. In testis, IL-11 mRNA is expressed in round spermatids at stage VI-IX seminiferous tubules. IL-11 expression in testis is restricted to developing spermatogonia and is developmentally regulated, since no expression is seen in mice genetically deficient in germ cells and in mice prior to sexual maturation. These expression data correlate with functional data demonstrating that IL-11 stimulates proliferation in vitro of a hippocampus neuronal progenitor cell line and administration of IL-11 in vivo accelerates recovery of spermatogenesis after cytotoxic therapy. These studies suggest that IL-11 may be an important regulator in neural and testicular function.

Murine interleukin-11 (IL-11) is expressed at high levels in the hippocampus and expression is developmentally regulated in the testis

IL-11, derived from a bone marrow stromal cell line, has pleiotropic effects on both hematopoietic cells and nonhematopoietic cells. However, no previous studies have systematically addressed expression of IL-11 in primary tissues in vivo and the relationship of IL-11 tissue specific gene expression and function of IL-11 is not clear. In the present study, we examined constitutive IL-11 expression in various murine adult tissues in vivo. IL-11 mRNA is expressed in a wide range of normal tissues (including hematopoietic organs) at levels only detected by RT-PCR. IL-11 protein was detected in brain and testis by Western blot analysis. The in vivo cellular distribution of IL-11 expression was examined by in situ hybridization. In brain, IL-11 message is distributed in granular layer dentate gyrus and pyramidal cell layers of hippocampus. IL-11 is also expressed in anterior horn cells and lateral column neuronal cells of the spinal cord. In testis, IL-11 mRNA is expressed in round spermatids at stage VI-IX seminiferous tubules. IL-11 expression in testis is restricted to developing spermatogonia and is developmentally regulated, since no expression is seen in mice genetically deficient in germ cells and in mice prior to sexual maturation. These expression data correlate with functional data demonstrating that IL-11 stimulates proliferation in vitro of a hippocampus neuronal progenitor cell line and administration of IL-11 in vivo accelerates recovery of spermatogenesis after cytotoxic therapy. These studies suggest that IL-11 may be an important regulator in neural and testicular function.

Xenogeneic expression of human stem cell factor in transgenic mice mimics codominant c-kit mutations

Mutations of c-kit, which encodes a transmembrane receptor tyrosine kinase, have been identified in mice by abnormal coat color, anemia, and germ cell defects. Mice heterozygous for mutations of c-kit have a white forehead blaze and a white ventral spot, leading these mutants to be termed dominant White spotting (W). We have previously demonstrated that the membrane-associated isoform of human stem cell factor (hSCF220, the ligand for c-kit) is inefficiently processed in murine stromal cell transfectants. Thus, in murine cell lines analyzed in vitro, hSCF220 transfectants present SCF as a membrane restricted protein in contrast to the murine SCF220 cDNA protein product, which is slowly cleaved and secreted. We show here that transgenic mice expressing the human SCF220 isoform in vivo display a phenotype indistinguishable from some alleles of W. Specifically, hSCF220-expressing transgenic mice display a prominent forehead blaze and a white ventral spot. Generations of doubly heterozygous animals that carry both a mutated c-kit allele and the hSCF220 transgene display a more severe coat color abnormality. This phenotype appears to be due to occupancy of murine c-kit by human SCF and diminished cell surface expression of endogenous murine SCF. Normal signaling events that lead to cell survival or proliferation appear to be disrupted in vivo in these transgenic mice.

Transforming growth factor-beta 1 and collagen gene expression during postnatal skin development and fibrosis in the tight-skin mouse

BACKGROUND

The tight-skin (Tsk) mutation in the mouse leads to widespread connective tissue abnormalities characterized by excessive collagen deposition that is similar to that observed in human scleroderma. Heterozygous mice develop skin fibrosis shortly after birth, providing a valuable model to investigate the sequence of events leading to fibrosis.

EXPERIMENTAL DESIGN

We have studied by in situ RNA hybridization the expression of procollagen alpha 1(I), alpha 1(III), alpha 2(VI) and transforming growth factor-beta 1 (TGF-beta 1) genes in the skin of Tsk mutant and normal newborn to aged mice. Tsk and normal skin sections at each age were mounted on the same slide to ensure identical experimental conditions, allowing for comparative analyses.

RESULTS

All genes are under temporospatial regulation and exhibit characteristic patterns of expression during postnatal skin growth and development. TGF-beta 1 mRNA is detected in fibroblasts only during the rapid postnatal growth of the skin in parallel with high collagen I, III, and VI gene expression. Collagen I and III gene-expressing fibroblasts are observed in excess in the Tsk fibrotic lesions. An abnormal pattern of collagen VI expression is only observed at later stages in the fibrotic process. Collagen VI shows a different expression pattern in both normal skin development and fibrosis, suggesting noncoordinate regulation with collagen I and III genes.

CONCLUSIONS

The fibrotic process in Tsk mice results from the persistence of high collagen I and III expression by a subpopulation of fibroblasts. Collagen VI overexpression participates later in the fibrotic process. In contrast with human scleroderma and other skin fibrotic diseases, TGF-beta 1 mRNA is not detected in the areas of abnormal collagen expression and fibrosis of Tsk. Alternative pathways should be explored to understand the abnormal extracellular matrix deposition of Tsk fibroblasts.

The role of mast cells in the development of skin fibrosis in tight-skin mutant mice

Chronic inflammatory conditions can evolve a fibrotic phenotype often associated with an increase in the number of mast cells (MC) near or within the granulation tissue. Despite the potential of MC to mediate fibrosis, it is unclear whether these cells play a central role in the pathogenesis of fibrosis or whether their presence is simply circumstantial. The tight-skin (Tsk) mouse develops an inherited fibrotic disease (sharing many similarities with the human disease scleroderma, systemic sclerosis) in which the lesions are associated with increased numbers and heightened granule release implicating MC in the pathogenesis of fibrosis. Despite their close association with the skin fibrosis of Tsk mice, the precise role of the MC in the pathogenesis of this inherited disease is unknown. Therefore, to assess directly whether MC are key elements in the pathogenesis of Tsk fibrosis, we generated MC deficient mice carrying the Tsk locus by utilizing selective interbreeding between Tsk and mutant mice deficient in mast cells (W, dominant white-spotting). We found that in the absence of MC, the early natural history of Tsk fibrosis was not altered. Furthermore, in older (5-7 months) Tsk mice, we found that the number of cutaneous MC was correlated with a more pronounced fibrosis. Therefore, we conclude that Tsk skin lesions are a pleiotropic manifestation of the Tsk gene in which MC are involved/recruited by an uncharacterized mechanism and that subsequent proliferation and activation of MC leads to augmentation of fibrosis.

Prevalence of p53 mutations in patients with squamous cell carcinoma of the esophagus

Squamous cell carcinoma of the esophagus has an uneven geographic distribution with a strong prevalence in the South Carolina Lowcountry. Although many environmental influences and some genetic factors have been implicated in its development, the molecular events required for tumorigenesis have not been defined. Point mutations in the p53 tumor suppressor gene are the most commonly noted genetic defect in human tumors. Our study shows that p53 point mutations occur more frequently in patients with esophageal cancer from this region than in patients from other areas of the world where the disease is prevalent.

Molecular cloning, tissue distribution, and expression of a 14-kDa bile acid-binding protein from rat ileal cytosol

A cDNA clone encoding the major intestinal cytosolic 14-kDa bile acid-binding protein (14-kDa I-BABP) was isolated from a rat ileal lambda gt22A library following immunoscreening using a monospecific antiserum raised against a 14-kDa polypeptide found in the rat ileal cytosol. One clone of 516 bp encoded a 128-amino acid protein with a predicted molecular mass of 14,544 Da. The deduced amino acid sequence of 14-kDa I-BABP showed 100% homology to rat intestinal 15-kDa protein (I-15P) and 72% homology to porcine 15-kDa gastrotropin, whereas comparison of I-BABP to rat 14-kDa fatty acid-binding proteins of liver, intestine, and heart revealed homologies of 44%, 25%, and 28%, respectively. Northern blot analysis revealed a single transcript of approximately 0.5 kb in ileum and ovary; however, the abundance of I-BABP mRNA was much greater in ileum than in ovary. No transcript was seen in RNA extracted from stomach, jejunum, colon, liver, adrenal, brain, heart, kidney, or testis. Transfection of the I-BABP cDNA into COS-7 cells resulted in the expression of a 14-kDa protein that was identical to the ileal cytosolic I-BABP as determined by immunoblotting. Photoaffinity labeling of expressed 14-kDa protein was saturable with respect to increasing concentrations of 7,7-azo[3H]taurocholate (Km, 83.3 microM; Vmax, 6.7 pmol/mg per 5 min). Taurocholate inhibited 7,7-azotaurocholate labeling by > 96% with lesser inhibition by taurochenodeoxycholate (83.1%), chenodeoxycholate (74.6%), cholate (50.5%), and progesterone (38.5%), whereas oleic acid and estradiol did not inhibit binding.

Flow cytometry. In vitro assessment of its potential application for diagnosis and classification of lymphoid processes in cytologic preparations from fine-needle aspirates

Detection and accurate classification of lymphoid processes in fine-needle aspirate specimens can be a challenging task for the pathologist. Recognizing the usefulness of flow cytometric methods for the diagnosis of lymphoproliferative disorders (LPDs), the authors applied flow cytometric analysis to 38 tissue samples that had a possible diagnosis of LPD and to fine-needle aspiration-derived cytologic preparations. Four aspirations from each sample provided from .44 x 10(6) to more than 70 x 10(6) cells in total. The highest yields were associated with low-grade B-cell non-Hodgkin's lymphomas (NHLs). Washing cytologic preparation cell suspensions did not enhance diagnostic ability and dramatically reduced cell counts (average decrease, 79.8%), potentially problematic with small samples. Comparison of ploidy, S fraction, and immunophenotypic data from the cytologic preparations and cell suspensions made from the conventionally processed parent tissues indicates that cytologic preparation composition closely parallels the tissue of origin. A multiparametric flow cytometric technique used to enhance detection of B-cell clonal expansions allowed for successful recognition of 17 of 21 (81%) B-cell NHLs in cytologic preparations, with false-negative results primarily reflecting a lack of viable tumor cells in the cytologic preparation cell suspensions. A T-cell NHL and a nonhematopoietic malignancy were also identified in cytologic preparations. None of the benign conditions were interpreted as lymphoma. Flow cytometric techniques applied to fine-needle aspirates of lymphoid processes yield important diagnostic information, which may be maximized by adaptations in processing and flow cytometric analysis.

Induction of erythrocyte HLA expression during interferon treatment and HIV infection

Although HLA antigens are present on the surface membrane of most cells, erythrocytes express little or no HLA. Occasionally red cells from normal individuals or patients with certain diseases express elevated levels of these molecules. The reasons for such variations are currently not understood. We report here that the expression of very high levels of HLA on erythrocytes occurs in response to interferon alpha given as a therapeutic agent for viral hepatitis. Increased expression became apparent after the second or third week of treatment, peaked at 3-4 months, and decreased at the end of the treatment period. This chronology suggests that elevated HLA expression is originated during erythropoiesis and persists throughout the lifetime of the erythrocyte. Furthermore, erythrocyte HLA expression did not correlate with changes of plasma HLA or beta 2-microglobulin concentrations and was not affected by in vitro chloroquine treatment, ruling out the possibility that HLA was adsorbed from plasma. Increased expression of HLA on erythrocytes was also demonstrated in patients infected with the human immunodeficiency virus, a disease in which increased production of endogenous interferon has been previously documented. We conclude that high HLA expression in red cells occurs in response to persistent interferon stimulation. Further studies will determine if this effect can also be produced by interferon tau or other factors.

Biclonal composite lymphoma. A multiparameter flow cytometric analysis

A case of composite, biclonal lymphoma detected and characterized by multiparameter flow cytometric analysis is presented. Analysis of cell surface immunophenotype and cell size, as assessed by forward light scatter, revealed that two populations of cells were present. The small cells were monoclonal kappa-positive cells admixed with reactive T and B cells. The large cells reacted solely with anti-lambda antibodies. Dual-color and dual-parameter (surface vs DNA) analysis further showed that the small, kappa-positive cells coexpressed CD5 and were diploid, with an estimated synthetic (S) fraction of 2.2%. The predicted histologic pattern was malignant lymphoma, small lymphocytic. In contrast, the large lambda-positive cells were both hyperdiploid and tetraploid with an estimated S fraction of 18%. On the basis of this multiparametric analysis, the predicted histologic pattern for the latter component was malignant lymphoma, diffuse large-cell type. Subsequent histologic examination confirmed the predicted pattern in both cases.

Class I HLA molecules on human erythrocytes. Quantitation and transfusion effects

HLA class I molecules were quantitated on erythrocytes from individuals expressing either high or low levels of such antigens. Quantitative determinations were accomplished using 125I-labeled Fab fragments of the anti-HLA monoclonal antibody W6/32 in a competitive binding assay. The experimental conditions of the test system were established using red cells from an individual found to express high levels of red cell HLA when examined by flow cytometry. The competitive binding assay met the requirements of ligand specificity and specific binding saturability. Scatchard analysis revealed that there were 1684 +/- 39 (mean +/- SD) HLA molecules/red cell. In two other donors in whom erythrocyte HLA was undetectable by flow cytometry specific binding of the 125I-W6/32 Fab fragments was clearly demonstrated, indicating the presence of HLA on red cells of these donors as well. The number of HLA molecules/red cell was estimated to be between 100 and 200 for these individuals. Thus, in a blood transfusion unit, the number of HLA molecules contributed by the red cells is comparable to that of the leukocytes. Blood highly depleted of leukocytes and platelets and selected from donors with low amounts of red cell HLA was not beneficial (when transfused to selected patients) in that their sensitizing effects were not significantly different from regular blood transfusions. These results show that the amount of HLA antigens on red cells, while low if compared with other cell types, is significant in terms of the absolute antigenic content of blood transfusions. They also show that transfusion of blood units containing HLA antigens in concentrations as low as can be achieved with current technology were not useful in preventing HLA sensitization in patients at risk.